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Topic Review (Newest First)

01-15-2013 06:27 AM

Minnewaska

Re: best way to mount Aluminium to steel underwater

I like the look of a sailboat with small decorative white lights under each spreader. They have a little bit of that "look at me" factor, but they serve a great purpose in identifying your boat among a hundred anchor lights at night. I've also seen a light installed under the boom to create a sort of night light, while walking through the cockpit. These seem classier to me than blue stinkpotter hull lights.

I have neither, but I do have the underwater lights installed by the prior owner. They aren't colored for decoration, they are underwater flood lights, which I've used on other boats in the Caribbean. Its like having your own aquarium at night. But up here, they are utterly useless and worry me.

01-15-2013 02:29 AM

xymotic

Re: best way to mount Aluminium to steel underwater

The ones I'm contemplating are blue, LED, and just fo augment other lights I'm putting on deck to make it kinda pretty at night. Or stupid/tacky depending on how you look at it I guess.

I'm a bit curious, what is the purpose of the underwater lights for you? One thing I have noticed with most that the customers are usually underwhelmed with what they see in the water. They are more decorative than anything, sort of like the under car lights, while most people seem to expect them to act as big spotlights to see lots of fish etc, or functional that they could see the bottom.
Especially if there's any pollution in the water, or boats with swim grids on the back, it doesn't look anything like the photos in the ads.
The latest ones we're using are these: OceanLED - Colours TH HD
they are a lot brighter, bronze and use a much smaller hole, with a synthetic spacer for metal hulls, power hungry though.
What about surface mounting them? If it's just for goofing around at anchor, you could put a magnet on a nice waterproof bright light and stick it over the side and have a useful tool in the meantime.

This sounds like a good idea, as the synthetic spacer would have to be very thick to protect it as salt water will act as the conductor. The only problem is that most of these lights need the water for cooling, so it would not be much use out of the water. They can be useful to attract fish, and I imagine lots of insects. In most waters it is too cloudy to see anything, so useless. Might help for diving to clear a prop. With the exception to attracting fish, these always seemed like the under car lights, and coffee can mufflers on cars, all show and nothing for go.

01-13-2013 12:47 AM

Jgbrown

Re: best way to mount Aluminium to steel underwater

I'm a bit curious, what is the purpose of the underwater lights for you? One thing I have noticed with most that the customers are usually underwhelmed with what they see in the water. They are more decorative than anything, sort of like the under car lights, while most people seem to expect them to act as big spotlights to see lots of fish etc, or functional that they could see the bottom.
Especially if there's any pollution in the water, or boats with swim grids on the back, it doesn't look anything like the photos in the ads.
The latest ones we're using are these: OceanLED - Colours TH HD
they are a lot brighter, bronze and use a much smaller hole, with a synthetic spacer for metal hulls, power hungry though.
What about surface mounting them? If it's just for goofing around at anchor, you could put a magnet on a nice waterproof bright light and stick it over the side and have a useful tool in the meantime.

01-12-2013 01:38 AM

xymotic

Re: best way to mount Aluminium to steel underwater

Thanks, great advice and looks like a good book

01-11-2013 07:10 AM

Maine Sail

Re: best way to mount Aluminium to steel underwater

Xymotic,

PLEASE, please, please before you do anything below water to your metal hull buy and read Everett Collier's book

Ed Sherman, the education director for the ABYC, recently wrote about a LARGE and EXPENSIVE motor yacht that sank due to its David Hasselhoff/Knight Rider under water lights, or as they are often affectionately refereed to as "look at me lights" .. Glug, glug, glug all because of corrosion.

This was the hole left in the vessel when the fixture completely eroded away due to corrosion. This boat sank due to corrosion of an under water light.

Image Courtesy Ed Sherman:

Not saying not to do this, just saying that you should FULLY EDUCATE yourself BEFORE doing this...

When you own a metal boat it is far more important for YOU to learn about corrosion than for others on the net to try and "tell" you about it. Please start with Everett's book....

01-11-2013 03:29 AM

mitiempo

Re: best way to mount Aluminium to steel underwater

I would use 3M 4200 or Sika 291

01-10-2013 09:59 PM

xymotic

Re: best way to mount Aluminium to steel underwater

I may rethink this and find an all plastic version instead. Seems safer.

But same question: If I drill & tap the hull, what's the best way to seal the thread and prevent galling? Something like permatex thread sealant, Tef Gel (water tight??) or 5200?

01-07-2013 12:02 PM

boatpoker

Re: best way to mount Aluminium to steel underwater

noelx77 is correct, done improperly this could sink your boat.

"electrolysis" is not the issue. Electrolysis is the chemical change in a solution or electrolyte due to the passage of electric current.

The potential problem here is "galvanic" corrosion and mixing steel, aluminum and DC current under water could cost you big time if not done properly. I strongly advise you to consult an ABYC certified electrician before proceeding.

There is no danger to the hull. The problem is the light is nice anode for the hull. If the aluminium light housing dissolves, which it will do sooner or later, you are left with a hole in hull underwater

Thanks, That is a concern indeed.

As for the actual hole for the wire, it can be pretty small, less 1/8" or so.

What would be the best way to seal it? Inject epoxy? Or am I over-thinking that as well and just use 5200?

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